Orthodontic appliance having continuous shape memory

ABSTRACT

Continuous adjustment appliances are provided that can store a large number of geometries that can be successively accessed throughout orthodontic treatment, with each geometry can correspond to an arrangement of the patient&#39;s teeth. An appliance according to the present disclosure can be stimulated to transition among the myriad geometries, which can include changes to the overall shape of the appliance as well as the position and geometry of the cavities corresponding to a patient&#39;s teeth. Methods of creating the continuous adjustment appliances and methods of treatment using the continuous adjustment appliances are also revealed.

BACKGROUND

Orthodontics is a specialized area of dentistry concerned with thediagnosis and treatment of dental malocclusions to improve bitefunction, hygiene, and facial aesthetics. Orthodontic therapy commonlyuses appliances called brackets and molar tubes which are bonded to apatient's teeth. Brackets and molar tubes contain slots and passageways,respectively, to accommodate a resilient “U”-shaped wire called anorthodontic archwire. During treatment, the archwire is secured withinthe slots and passageways of the brackets and molar tubes. While thearchwire is initially distorted, it gradually returns to its originalshape over the course of treatment, thereby applying therapeutic forcesto urge the malpositioned teeth to proper locations.

Another type of orthodontic treatment involves the use of resilientpolymeric trays that fit over the teeth of the patient's dental arches.These trays, also known as aligners, alignment shells and polymericappliances, are provided in a series and are intended to be worn insuccession in order to gradually move the teeth in incremental stepstoward a desired target arrangement. Some types of polymeric applianceshave a row of tooth-shaped cavities for receiving each tooth of thepatient's dental arch, and the cavities are oriented in slightlydifferent positions from one appliance to the next in order toincrementally urge each tooth toward its desired target position byvirtue of the resilient properties of the polymeric material.

A variety of methods have been proposed for manufacturing polymericappliances. According to one known method, a digital data file isobtained that represents the patient's upper and lower dental arches atthe beginning of treatment. This data file is then analyzed to identifysubsets of data, each of which represents one of the patient's teeth.Next, a technician then uses a computer input device (such as a mouse orkeyboard) to virtually reposition the maloccluded teeth and moveindividual teeth on a computer screen relative to each other intodesired target positions. The target positions are then reviewed andapproved by a treating professional, such as an orthodontist that islocated remotely from the technician.

Once the proposed tooth arrangement has been approved, the datarepresenting the initial tooth positions and the data representing thetarget tooth positions are then used to determine intended intermediatepositions of the teeth as the teeth move from initial to targetpositions. As one example, data representing the differences in toothpositions between the initial tooth arrangement and the target tootharrangement may be interpolated in order to obtain a series of twentyintermediate positions of the teeth. The data representing thoseintermediate tooth positions is then stored in memory and subsequentlyused to make models of the dental arches for each intermediate tootharrangement.

For example, a data set representing the teeth in a desired targetarrangement and twenty data sets representing the teeth in twentydifferent intermediate arrangements may be used to manufacture a seriesof twenty-one physical, positive dental arch models for each dental archusing rapid prototyping methods such as stereolithography. Subsequently,a sheet of polymeric material is placed over each of the arch models andformed under heat, pressure and/or vacuum to conform to the model teethof each model arch. The formed sheet is cleaned and trimmed as neededand the resulting arch-shaped appliance is shipped along with theremaining appliances to the treating professional. The patient is theninstructed to wear each appliance over its intended dental arch insequence for a period of, for example, two or four weeks, after whichthe used appliances are discarded and the next two appliances in theseries for the upper and lower dental arches are to be worn.

SUMMARY OF THE INVENTION

Typical polymeric appliances are configured to store one or two shapescorresponding to different arrangements of the patient's teeth. Thisrequires the patient to continually replace the worn appliance with asubsequent appliance to ensure the application of continued, clinicallyeffective force on the relevant teeth. Such limited shape storage alsorequires that any given appliance only move the teeth a limited amount(e.g., 0.2 mm), and particularly complicated malocclusion may require anexcess number of appliances to treat. In contrast, the presentdisclosure provides continuous adjustment appliances that can store alarge number of geometries that can be successively accessed throughouttreatment. Each geometry can correspond to an arrangement of thepatient's teeth. An appliance according to the present disclosure can bestimulated to transition among myriad geometries, which can includechanges to the overall shape of the appliance as well as the positionand geometry of the cavities corresponding to a patient's teeth. Thisvariability allows the patient or practitioner to vary the differencesbetween given successive tooth arrangements to expand or contract thelength of time the patient wears a given configuration before needing totransition to the next appliance configuration. In some embodiments, theappliance can be manufactured to store at least 4, at least 6, at least10, at least 20, and at least 30 distinct appliance geometries. Theability to store multiple geometries in a single appliance is a distinctadvantage, as it allows for more iterations of movement between anygiven tooth orientation. This can have the effect of both makingtreatment more efficient, in certain implementations, as well asimproving comfort for the patient. Appliances of the present disclosurecan also be formed from materials that are softer than typically used tocreate polymeric appliances, which can also lead to an increase inpatient comfort and compliance. Furthermore, by requiring fewerappliances to perform the same treatment goals, the continuousadjustment appliances of the present disclosure can reduce the materialand manufacturing cost associated with any given treatment.

In one aspect, the present disclosure provides a polymeric shell dentalappliance for placement on a dental arch comprising a concave troughhaving cavities configured to be positioned on a plurality of teeth inthe dental arch and having a first approximate shape, wherein theconcave trough comprises a crosslinked shape memory polymer, and whereinthe crosslinked shape memory polymer is a semicrystalline, non-segmentedpolymer configured to restore the concave trough to (a) a secondapproximate shape on application of a first external energy stimulus;and (b) a third approximate shape on application of a second externalenergy stimulus of a greater magnitude than the first energy stimulus.

In another aspect, the present disclosure provides a method formanufacturing polymeric dental appliances configured to conform to oneor more teeth of a patient. The method comprises providing a firstpositive model of the patient's dentition, the model representing arepositioned arrangement of the patient's teeth and forming over themodel at a first molding temperature a sheet of crosslinkable,crystallizable polymeric material having a crystallization temperaturerange having an upper limit and a lower limit. The method next involvescrosslinking the polymer to create an appliance having a first storedgeometry. Next, a second model representing a first intermediatearrangement of the patient's teeth is provided, with the arrangementincluding one or more teeth in different orientations than the firstmodel. The appliance is subjected to a second molding temperature withinthe crystallization temperature range to create an appliance having asecond stored geometry. The method next includes the steps of providinga third model representing a second intermediate arrangement of thepatient's teeth, the second arrangement including one or more teeth indifferent orientations than the first intermediate arrangement,subjecting the appliance to a third molding temperature within thecrystallization temperature range to create a third stored geometry, thethird molding temperature being less than either the first or secondmolding temperatures; and cooling the appliance below the lower limit oftransition temperature range.

In yet another aspect, the present disclosure provides a method ofmoving a patient's teeth of a target arrangement. The method includesplacing a polymeric dental appliance having a first configuration on adental arch, the polymeric appliance comprising a crosslinked,semicrystalline shape memory polymer having a number of crosslinks andcrystalline structures; heating the appliance to a first transitiontemperature so as to modify the shape of the appliance to a secondconfiguration. Once the appliance reaches the second configuration, itis placed on the dental arch. Subsequently, the appliance is heated to asecond transition temperature so as to modify the shape of the shell toa third configuration. The polymeric appliance in the thirdconfiguration is placed on the dental arch, with the third configurationshaped to reposition the patient's teeth to the target arrangement.

As used herein, a “cross-linking polymeric material” means a polymer,for example polyethylene, that can be cross-linked by a variety ofapproaches, including those employing cross-linking chemicals (such asperoxides and/or silane) and/or irradiation. Preferred approaches forcross-linking employ irradiation.

The words “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the disclosure.

In this application, terms such as “a”, “an”, and “the” are not intendedto refer to only a singular entity, but include the general class ofwhich a specific example may be used for illustration. The terms “a”,“an”, and “the” are used interchangeably with the term “at least one.”The phrases “at least one of” and “comprises at least one of” followedby a list refers to any one of the items in the list and any combinationof two or more items in the list.

As used herein, the term “or” is generally employed in its usual senseincluding “and/or” unless the content clearly dictates otherwise.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements.

Also herein, all numbers are assumed to be modified by the term “about”and preferably by the term “exactly.” As used herein in connection witha measured quantity, the term “about” refers to that variation in themeasured quantity as would be expected by the skilled artisan making themeasurement and exercising a level of care commensurate with theobjective of the measurement and the precision of the measuringequipment used.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range as well as the endpoints (e.g., 1to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

As used herein as a modifier to a property or attribute, the term“generally”, unless otherwise specifically defined, means that theproperty or attribute would be readily recognizable by a person ofordinary skill but without requiring absolute precision or a perfectmatch (e.g., within +/−20% for quantifiable properties). The term“substantially”, unless otherwise specifically defined, means to a highdegree of approximation (e.g., within +/−10% for quantifiableproperties) but again without requiring absolute precision or a perfectmatch. Terms such as same, equal, uniform, constant, strictly, and thelike, are understood to be within the usual tolerances or measuringerror applicable to the particular circumstance rather than requiringabsolute precision or a perfect match.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a continuous adjustment applianceaccording to one embodiment of the present disclosure;

FIG. 2 is a flowchart of a process for designing and manufacturing acontinuous adjustment appliance according to the present disclosure:

FIG. 3 is a flowchart of a process for specifying a treatment planleveraging the adjustment appliances of the present disclosure;

FIG. 4 is a flowchart of a process for manufacturing a continuousadjustment appliance based on a plurality of dental arrangementsaccording to the present disclosure;

FIG. 5 is a perspective view of a system for making an adjustmentappliance in accordance with one embodiment of the disclosure;

FIG. 6 is a flowchart of a process for manufacturing a continuousadjustment appliance using the system of FIG. 5; and

FIG. 7 is a flowchart for treating a patient using a continuousadjustment appliance according to the present disclosure.

While the above-identified figures set forth several embodiments of thedisclosure other embodiments are also contemplated, as noted in thedescription. In all cases, this disclosure presents the invention by wayof representation and not limitation. It should be understood thatnumerous other modifications and embodiments can be devised by thoseskilled in the art, which fall within the scope and spirit of theprinciples of the invention.

Directional Definitions

-   As used herein:-   “Mesial” means in a direction toward the center of the patient's    curved dental arch.-   “Distal” means in a direction away from the center of the patient's    curved dental arch.-   “Occlusal” means in a direction toward the outer tips of the    patient's teeth.-   “Gingival” means in a direction toward the patient's gums or    gingiva.-   “Facial” means in a direction toward the patient's lips or cheeks.-   “Lingual” means in a direction toward the patient's tongue.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure provides continuous adjustment appliances thatcan store a large number of geometries that can be successively accessedthroughout treatment. Each geometry can correspond to an arrangement ofthe patient's teeth. In typical treatment, each arrangement of teethrequires the use of a new appliance. In contrast, an appliance accordingto the present disclosure can be stimulated to transition among myriadgeometries, which can include changes to the overall shape of theappliance as well as the position and geometry of the cavitiescorresponding to a patient's teeth.

One implementation of a continuous adjustment appliance is generallydepicted in FIG. 1. The continuous adjustment appliance 100 is removableand replaceable over the teeth. In some embodiments, appliance 100 isone of a plurality of incremental adjustment appliances. The continuousadjustment appliance 100 may comprise a polymeric concave trough havingan inner cavity. The inner cavity is shaped to receive and resilientlyreposition teeth from one tooth arrangement to a successive tootharrangement. The inner cavity may include a plurality of receptacles,each of which is adapted to connect to and receive a respective tooth ofthe patient's dental arch. The receptacles are spaced apart from eachother along the length of the cavity, although adjoining regions ofadjacent receptacles can be in communication with each other. In someembodiments, the polymeric concave trough fits over all teeth present inthe upper jaw or lower jaw. Typically, only certain one(s) of the teethwill be repositioned while others of the teeth will provide a base oranchor region for holding the dental appliance in place as it appliesthe resilient repositioning force against the tooth or teeth to berepositioned. The continuous adjustment appliances of the presentdisclosure can also take the form of other polymeric orthodonticappliances typically worn in series, including, for example, the springaligners and other appliances described in International Publication No.WO2016/109660 (Raby et al.), as well as those described in WO2016/149007(Oda et al.) and WO2016/148960 (Cinader et al.).

The continuous adjustment appliances can rely on certain shape memorypolymer concepts to transition between stages. Shape memory polymers areknown to have the unique ability to be set in a pre-set shape, deformedto an altered shape, and then revert back to the pre-set shape whenexposed to the appropriate stimuli (e.g., changes in temperature,application of solvent, etc.). When processed according to the methodsdescribed therein, orthodontic appliances comprising shape memorypolymers can revert back to a plurality of pre-set shapes upon exposureto staged external stimuli. For example, the orthodontic appliance mayinclude a shape memory polymer surface that has been cast or otherwiseshaped to have a permanent shape or configuration. As another example,an entire appliance may consist of shape memory polymer storing aplurality of geometries. This surface can be deformed to an altered ordeformed shape and then be shifted back or recovered to the permanentshape when appropriately triggered. Triggering the shift from thedeformed shape to the permanent shape can vary depending on theparticular polymer used or other parameters. However, at least some ofthe shape memory polymers disclosed herein can be shifted by exposure toelevated temperatures and/or to an appropriate solvent.

Shape memory polymers can be classified as elastomers. On the molecularlevel they represent polymer networks that include segment chains thatare connected by netpoints. The netpoints can be formed by entanglementsof the polymer chains or intermolecular interaction of certain polymerblocks. These cross-links are called physical netpoints. Crosslinks inthe form of covalent bonds form chemical netpoints. An elastomerexhibits a shape-memory functionality if the material can be stabilizedin the deformed state in a temperature range that is relevant for theparticular application. This can be achieved by using the network chainsas a kind of molecular switch. For this purpose, it should be possibleto limit the flexibility of the segments as a function of temperature.The ability to incorporate a control function into the material providesa thermal transition T_(trans) of the network chains in the temperaturerange of interest for the particular application. At temperatures aboveT_(trans) the chain segments are flexible, whereas the flexibility ofthe chains below this thermal transition is at least partially limited.In the case of a transition from the rubber-elastic, i.e., viscous, tothe glassy state the flexibility of the entire segment is limited.

SMPs have a defined melting point (T_(m)) or glass transitiontemperature (T_(g)). Collectively, the melting point (T_(m)) or glasstransition temperature (T_(g)) will be referred to as the transitiontemperature or T_(trans). Above the T_(trans) the polymers areelastomeric in nature, and are capable of being deformed with highstrain. The elastomeric behavior of the polymers results from eitherchemical crosslinks or physical crosslinks (often resulting frommicrophase separation). Therefore, SMPs can be glassy or crystalline andcan be either thermosets or thermoplastics. SMPs particularly useful inthe present disclosure are semicrystalline and contain chemicalcrosslinks.

Without being bound to theory, it is believed that the crystallinedomains hold or constrain molecular mobility, so the polymer maintains adeformed shape. Shifting from a deformed shape to the original orpermanent shape generally includes mobilizing at least a portion of thecrystalline domains of the shape memory polymer in order to allow thepolymer to elastically “spring back” or otherwise shift to the originalpermanent shape. According to this theory, mobilizing is understood tobe the mobilization of the crystalline phase through the application ofthe appropriate external stimuli. Not all of the crystalline domainsneeds to be mobilized at one time, and progressive increases intemperature can yield multiple intermediate shapes as the polymertransitions from first deformed state to the original or permanentshape. Such selective mobilization provides for the retention of aplurality of shapes in single structure.

SMPs particularly useful in the present disclosure exhibit a relativelybroad crystallization temperature range over which the SMP forms a rangeof crystalline domains. As used herein, the crystallization temperaturerange refers to a range of temperatures below the T_(trans) in which theSMP exhibits significant crystal growth. The crystallization temperaturerange is dependent upon, among other factors, the processing and thermalhistory of the SMP. For example, polyethylene can have a crystallizationtemperature range of about 60° C. to about 120° C. The crystallizationrange can also be influenced by the molecular architecture of thepolymer. For example, branchpoints in the SMP polymer backbone andcomonomer incorporation can decrease the crystallinity overall anddepress the crystallization temperature range relative to pure, linearpolymer.

In presently preferred implementations, the crystallization temperaturerange has a lower bound substantially above body temperature (37° C.).In such implementations, the polymer is unlikely to undergo a change inconfiguration once the appliance is placed on the dental arch. In someor all embodiments, the lower limit of the crystallization temperaturerange is at least 55° C., at least 60° C., or at least 65° C. Further,the upper boundary of the crystallization temperature range issubstantially below the temperature necessary to disrupt crosslinksformed in the SMP. In some or all embodiments, the upper limit of thecrystallization temperature range is no greater than 135° C., no greaterthan 130° C., or no greater than 125° C. The crystallization temperaturerange of a polymer suitable for use in present disclosure generallyoverlaps with the melting temperature range of that polymer. In suchcircumstances, there may be some differences depending on whethercrystals are being formed or destroyed according to the methodsdescribed herein, but the two ranges are generally interchangeable.

Crystalline structures formed at a plurality of different moldtemperatures are useful for storing a plurality of geometries in anappliance of the present disclosure. Crystalline structures formed atthe lower bound of the crystallization temperature range can bedisrupted when heated above the formation (i.e., molding) temperaturereached in creating the crystals, while crystalline structures formed atthe higher temperature remain essentially in place. Upon cooling, theremaining crystalline structures can define a new geometry for theappliance.

The permanent, original shape of the SMP is established when therequisite crosslinks are formed during or after an initial moldingprocess. After crosslinking, the SMP can then be deformed from theoriginal shape to a plurality of temporary shapes. The temporary shapesare often set by heating the polymer at a temperature within itscrystallization temperature range and deforming the sample, and thenholding the deformation in place while the SMP cools. The formation ofcrystalline structures at the corresponding molding temperature holdsone temporary shape. The next and subsequent successive temporary shapesare stored by heating the polymer at progressively lower temperaturewithin the SMP's crystallization temperature range and again deformingthe sample into a new geometry, and then holding the deformation inplace while the SMP cools. Subsequently, the original shape is recoveredby heating the material above the highest molding temperature.

In presently preferred embodiments, the shape memory polymer is across-linking semi-crystalline elastomer. Many suitable semi-crystallinepolymers for use in the present invention are initially non-crosslinkedlong chain molecules, including polyethylene (low and high density),ultra-high molecular weight polyethylene, polypropylene, nylon, andethylene vinyl acetate (EVA) among others. In some cases, polyethylenehomopolymer may be preferred due to its appropriate crystallizationtemperature range and its ability to be readily crosslinked byirradiation. In some embodiments the shape memory polymer compositionmay be cast into a permanent shape and deformed to a plurality oftemporary shapes at a plurality of temperatures below the T_(trans) sothat each deformed temporary shape is retained or locked in despiteother configurations formed at higher temperatures. When the deformedarticle is heated above a preset molding temperature, the deformedarticle will elastically recover a successive shape or permanent shape.The process may be repeated, as described below, at multipletemperatures.

To prepare an appliance having the type of shape memory described, theappliance can be molded and crosslinked to form a permanent shape. Theappliance is subsequently deformed into two or more temporary shapes bymolding and heating the appliance at a series of temperatures below theT_(trans) in a plurality of modified geometries relative to the originalshape. The disparate molding temperatures define a step wise sequence oftransitions, creating a crystalline region with a plurality of melttemperatures. The appliance can be returned to any shape in the sequenceand ultimately its original permanent shape by heating the object abovethe molding temperature of the preceding appliance geometry in thesequence or T_(trans). In other embodiments, a solvent such as alkylalcohol, acetone, etc. can partially dissolve or plasticize thecrystalline phase of thermoplastic SMPs and cause the same recovery.

Referring to FIG. 2, a method 200 of creating a continuous memoryappliance according to the present disclosure is illustrated. Individualaspects of the process are discussed in further detail below. Theprocess includes generating a treatment plan for repositioning apatient's teeth. Briefly, a treatment plan will include obtaining datacomprising an initial arrangement of the patient's teeth (Step 202),which typically includes obtaining an impression or scan of thepatient's teeth prior to the onset of treatment. The treatment plan willalso include identifying a final or target arrangement of the patient'steeth that is desired (Step 204), as well as a plurality of plannedsuccessive or intermediary tooth arrangements for moving the teeth alonga treatment path from the initial arrangement toward the selected finalor target arrangement (206). A series of physical model representationsof the successive tooth arrangements (up to and including the targetarrangement) are then created based on the treatment plan (Step 208). Anappliance can be generated based on three or more of the positive dentalmodel representations and administered to the patient (Step 210).

A continuous adjustment appliance can be designed and/or provided as asingle appliance or as part of a set or plurality of appliances. Eachappliance or appliance configuration may be configured so atooth-receiving cavity has a geometry corresponding to an intermediateor final tooth arrangement intended for the appliance. The patient'steeth can be progressively repositioned from an initial tootharrangement to a target tooth arrangement by modifying the geometry ofthe continuous adjustment appliance (e.g., the tooth-receiving cavitygeometry) over the patient's teeth. A target tooth arrangement can be aplanned final tooth arrangement selected for the patient's teeth at theend of all planned orthodontic treatment. Alternatively, a targetarrangement can be one of many intermediate arrangements for thepatient's teeth during the course of orthodontic treatment. As such, itis understood that a target tooth arrangement can be any plannedresulting arrangement for the patient's teeth that follows one or moreincremental repositioning stages. Likewise, an initial tooth arrangementcan be any initial arrangement for the patient's teeth that is followedby one or more incremental repositioning stages. The appliances can begenerated all at the same time or in sets or batches. The patient wearseach appliance for a fixed length of time as instructed by theirprescribing doctor. A plurality of different appliance configurationscan be designed and fabricated prior to the patient wearing theappliance or any appliance of the series of appliances according tomethods further specified below. After wearing an applianceconfiguration for an appropriate period of time, the patient replacesthe current appliance configuration with the next applianceconfiguration or next appliance in the series until the prescribed ordesired number of appliances in the series have been worn. Additionalseries of appliances may be fabricated and worn until a satisfactorytreatment outcome is achieved.

An adjustment appliance can generated at the beginning of the treatmentas an individual appliance or part a series of appliances, and thepatient wears the appliance until the pressure of the appliance on theteeth can generally no longer be felt. At that point, the patientreplaces the current adjustment appliance with the next applianceconfiguration (e.g., the successive stored geometry in the currentappliance or a new appliance) in the series until no more applianceconfigurations remain. The final appliance or several appliances in theseries may have a geometry or geometries selected to overcorrect thetooth arrangement, i.e., have a geometry which would (if fully achieved)move individual teeth beyond the tooth arrangement which has beenselected as the “final.” Such overcorrection may be desirable in orderto offset potential relapse after the repositioning method has beenterminated, i.e., to permit some movement of individual teeth backtoward their precorrected positions. Overcorrection may also bebeneficial to speed the rate of correction, i.e., by having an appliancewith a geometry that is positioned beyond a desired intermediate orfinal position, the individual teeth will be shifted toward the positionat a greater rate. In such cases, the use of an appliance can beterminated before the teeth reach the positions defined by theappliance.

Generating the Treatment Plan

FIG. 3 illustrates the general flow of an exemplary process 300 fordefining and generating a treatment plan, including repositioningappliances for orthodontic treatment of a patient. The steps of theprocess can be implemented as computer program modules for execution onone or more computer systems. Systems and methods for generating atreatment plan can be found, for example, in U.S. Pat. No. 7,435,083(Chisti et al.), U.S. Pat. No. 7,134,874 (Chisti et al.), U.S. PatentPublication Nos. 2009/0286196 (Wen et al.); 2010/0260405 (Cinader) andU.S. Pat. No. 9,259,295 (Christoff et al.).

As an initial step, a mold or a scan of patient's teeth or mouth tissueis acquired (Step 302). This generally involves taking casts of thepatient's teeth and gums, and may in addition or alternately involvetaking wax bites, direct contact scanning, x-ray imaging, tomographicimaging, sonographic imaging, and other techniques for obtaininginformation about the position and structure of the teeth, jaws, gumsand other orthodontically relevant tissue. A digital data set is derivedfrom this data that represents an initial (e.g., pretreatment)arrangement of the patient's teeth and other tissues. A computer modelof the arch may then be re-constructed based on the scan data.

One exemplary technique is digital scanning. A virtual dental modelrepresenting the patient's dental structure can be captured using adigital intraoral scan or by digitally scanning an impression or dentalmodel. The digital images may be provided using a hand-held intra-oralscanner such as the intra-oral scanner using active wavefront samplingdeveloped by Brontes Technologies, Inc. (Lexington, Mass.) anddescribed, e.g., in PCT Publication No. WO 2007/084727 (Boerj es etal.). In one or more embodiments, other intra-oral scanners orintra-oral contact probes may be used. As another option, the digitalstructure data may be provided by scanning a negative impression of thepatient's teeth. As still another option, the digital structure data maybe provided by imaging a positive physical model of the patient's teethor by using a contact probe on a model of the patient's teeth. The modelused for scanning may be made, for example, by casting an impression ofa patient's dentition from a suitable impression material such asalginate or polyvinylsiloxane (PVS), pouring a casting material (such asorthodontic stone or epoxy resin) into the impression, and allowing thecasting material to cure. Any suitable scanning technique may be usedfor scanning the model, including X-ray radiography, laser scanning,computed tomography (CT), magnetic resonance imaging (MRI), andultrasound imaging. Other possible scanning methods are described, e.g.,in U.S. Patent Application Publication No. 2007/0031791 (Cinader, etal.).

The initial digital data set, which may include both raw data fromscanning operations and data representing surface models derived fromthe raw data, can be processed to segment the tissue constituents fromeach other (Step 304), including defining discrete dental objects. Forexample, data structures that digitally represent individual toothcrowns can be produced. In some embodiments, digital models of entireteeth are produced, including measured or extrapolated hidden surfacesand root structures.

Desired final positions of the teeth, or tooth positions that aredesired and/or intended end result of orthodontic treatment, can bereceived, e.g., from a practitioner in the form of a descriptiveprescription, can be calculated using basic orthodontic prescriptions,or can be extrapolated computationally from a clinical prescription(Step 306). With a specification of the desired final positions of theteeth and a digital representation of the teeth themselves, the finalposition and surface geometry of each tooth can be specified (Step 308)to form a complete model of the teeth at the desired end of treatment ortreatment stage. The result of this step is a set of digital datastructures that represents a desired and/or orthodontically correctrepositioning of the modeled teeth relative to presumed-stable tissue.The teeth and surrounding tissue can both be represented as digitaldata. Further details on software and processes that may be used toderive the target dental arrangement are disclosed, e.g., in U.S. Pat.No. 6,739,870 (Lai et al.), and U.S. Pat. Nos. 8,194,067; 7,291,011;7,354,268; 7,869,983 and 7,726,968 (Raby et al.).

Having both a beginning position and a final target position for eachtooth, the process next defines a treatment path or tooth path for themotion of each tooth (Step 310). This includes defining a plurality ofplanned successive tooth arrangements for moving teeth along a treatmentpath from an initial arrangement to a selected final arrangement. In oneembodiment, the tooth paths are optimized in the aggregate so that theteeth are moved in the most efficient and clinically acceptable fashionto bring the teeth from their initial positions to their desired finalpositions.

A movement pathway for each tooth between a beginning position and adesired final position may be calculated based on a number ofparameters, including the total distance of tooth movement, thedifficulty in moving the teeth (e.g., based on the surroundingstructures, the types and locations of teeth being moved, etc.) andother patient-specific data that may be provided. Based on this sort ofinformation, a user or a computer program may generate an appropriatenumber of intermediary steps (corresponding to a number of treatmentsteps). In some variations, the user may specify a number of steps, andthe software can map different appliance configurations accordingly.Alternatively, the movement pathway may be guided by (or set by) theuser.

If the movement path requires that the teeth move more than apredetermined amount (e.g., 0.3 mm or less in X or Y translation), thenthe movement path may be divided up into multiple steps, where each stepcorresponds to a separate target arrangement. The predetermined amountis generally the amount that an appliance or appliance configuration canmove a tooth in a particular direction in the time required for eachtreatment step. Each appliance configuration corresponds to a plannedsuccessive arrangement of the teeth, and represents a step along thetreatment path for the patient. For example, the steps can be definedand calculated so that each discrete position can follow bystraight-line tooth movement or simple rotation from the tooth positionsachieved by the preceding discrete step and so that the amount ofrepositioning required at each step involves an orthodontically optimalamount of force on the patient's dentition. As with other steps, thiscalculation step can include interactions with the practitioner (Step312).

At various stages, the process can include interaction with apractitioner responsible for the treatment of the patient (Step 312).Practitioner interaction can be implemented using a client processprogrammed to receive tooth positions and models, as well as pathinformation from a server computer or process in which other steps ofprocess 300 are implemented. In some or all embodiments, the treatmentplanning described with respect to FIG. 3 may be embodied within acomputer-readable storage medium, such as a computer-readable storagemedium of clinician's computing device and/or manufacturer's computer,or both. The computer-readable storage medium stores computer-executableinstructions that, when executed, configure a processor to perform themodel preparation and treatment planning techniques described above.

A completed treatment plan for use in manufacturing the appliances ofthe present includes a plurality of successive arrangements between aninitial arrangement and the desired final arrangement. The plurality ofsuccessive dental arrangements may be incorporated into a singleappliance or apportioned between multiple appliances to be worn inseries. Accordingly, a suitable treatment plan identifies a number ofappliances in an acceptable series, as well as a target arrangement anda commencing arrangement for each appliance in the series. A pluralityof planned, successive arrangements may be stored between the target andthe commencing arrangements. As defined herein, the “target arrangement”may be a desired final dental arrangement or a planned successive dentalarrangement the patient should reach after treatment with the appliance.In contrast, the “commencing arrangement” is the dental arrangement theappliance is configured to represent when the appliance is first placedin the patient's mouth. As such, it is closest in orientation to theinitial or current arrangement of the patient's teeth, and in someembodiments represents the current arrangement.

Manufacturing the Appliance

Continuous memory appliances can be formed by incorporating a pluralityof planned successive tooth arrangements into a single appliancestructure. While typical appliances are formed in stages progressingfrom the patient's current arrangement to a target arrangement, thecontinuous memory appliances of the present disclosure are initiallyformed to approximate the target tooth arrangement. Additional shapesare added to the appliance in regressive fashion, working backward fromthe target arrangement to the commencing arrangement of the treatmentplan. By manufacturing the appliances in this way, the patient orpractitioner may unlock the next phase of treatment by triggering achange in the shape of the appliance from the commencing arrangement tothe next successive arrangement until the target arrangement is reached.

A general process 400 for creating a continuous memory appliance isillustrated in FIG. 4. One, some, or all of the steps of method 400 maybe performed in a temperature and pressure controlled chamber. At theoutset, a physical, dental model of the patient's teeth in a targetarrangement is provided (Step 402). A sheet of semicrystalline polymericmaterial is provided and placed over the dental model. (Step 404). Atthis stage, the semicrystalline, polymeric material is substantiallynon-crosslinked. The model and the sheet of material are placed under afirst pressure and heated to a first temperature near, but preferablybelow, the melt temperature of the polymer (Step 406). The combinationof heat and pressure/or vacuum causes the material to soften. The modeland sheet are maintained at the first temperature and pressure untilsuch time as the sheet has conformed to the shape and orientation of thedental model and crystalline structures in the polymer have melted. Thetemperature is subsequently decreased (preferably isobarically) tocreate a shell appliance in a configuration having a first storedgeometry corresponding to the dental arrangement of the first model(Step 408). The shell appliance is subsequently crosslinked, inpresently preferred circumstances using ionizing radiation. (Step 410).The crosslinked shell in a configuration having the first storedgeometry now represents the original shape of the appliance.

In some embodiments, the polymeric material is heated to a temperatureabove the upper range of its crystallization temperature and potentiallyabove the T_(trans,) for example, about 120° C., about 130° C., about140° C., during the forming process of Step 406. Preferably, the firsttemperature is below the melting temperature of the semicrystallinepolymeric material, typically about 25° C. below to about 0.5° C. below.However, various temperatures and times may be utilized.

In some embodiments, the pressure applied is greater than 10 kPa, e.g.,greater than 50 kPa, 75 kPa, 100 kPa, 125 kPa, or greater than 150 kPa.In some embodiments, the pressure is maintained for greater than 30seconds, e.g., greater than 45 seconds, 60 seconds, 2.5 minutes, 5.0minutes, 10 minutes, 20 minutes, 30 minutes, 60 minutes, greater than 90minutes, or even greater than 120 minutes, before release of pressureback to nominal atmospheric pressure. The pressure may be applied bydirect force on the polymeric material and/or vacuum.

A first plurality of crystalline structures are formed in the polymericmaterial as the temperature is reduced from first molding temperature toa subsequent temperature (e.g., room temperature) in step 408. Thecrystalline structures formed hold the appliance in the first storedgeometry prior to irradiation or other suitable method of creatingcrosslinks in the polymeric material. In some or all embodiments, thetemperature is gradually reduced. In other embodiments, appliance may bequenched by rapid reduction in temperature. In any event, it ispresently preferred that the parameters selected remain consistent foreach relevant step in the process. For example, the rate of temperaturereduction could be in the range of about 0.5° C. to about 10° C. perminute, but is typically held at the same rate within the range for eachtemperature reduction step in the process 400.

Irradiation, if used to crosslink the material, can be done at roomtemperature or at elevated temperatures typically below the firstmolding temperature. Irradiation can be performed in air, in vacuum, orin oxygen-free environment, including inert gases such as nitrogen ornoble gases. Irradiation can be performed by using electron-beam, gammairradiation, or x-ray irradiation. In some embodiments, an ionizingradiation (e.g., an electron beam, x-ray radiation or gamma radiation)is employed to crosslink the non-segmented, polymeric material. Inspecific embodiments, gamma radiation is employed to crosslink thesubstantially non-crosslinked polymeric material. In some embodiments,the irradiating (with any radiation source) is performed until thesample receives a dose of at least 0.25 Mrad (2.5 kGy), e.g., at least1.0 Mrad (10 kGy), at least 2.5 Mrad (25 kGy), at least 5.0 Mrad (50kGy), or at least 10.0 Mrad (100 kGy). In some embodiments, theirradiating is performed until the sample receives a dose of between 1.0Mrad and 6.0 Mrad, e.g., between 1.5 Mrad and 4.0 Mrad.

In other embodiments, the appliance is treated to create chemicalcrosslinks using methods known in the art. For example, peroxides can beadded to the polymer, and the polymer can be maintained at an elevatedtemperature after forming into the first stored geometry to allow theperoxides to react. In addition, silanes can be grafted to a polymerbackbone, such as polyethylene, and the polymer can be crosslinked uponexposure to a hot, humid environment.

The thickness of the semicrystalline polymer sheet is chosen to providea clinically appropriate thickness of the material in the resultantappliance. The thickness of the material should typically be selectedsuch that the memory appliance is stiff enough to apply sufficient forceto the teeth, but remains thin enough to be comfortably worn. Thethickness of the walls of the appliance may be between 0.05 mm and 2 mm,or between 0.1 mm and 1 mm.

Referring again to FIG. 4, a second physical, dental model of thepatient's teeth in a least one successive arrangement from the patient'streatment plan is provided (Step 420). The second arrangement includes aleast one tooth in a different position or orientation than the sametooth in the first model. The second dental model is a second storablegeometry representing an arrangement of the patient's teeth between theinitial arrangement and the first arrangement, and includes teeth inpositions or orientations between the target arrangement and initialarrangement. Starting from the initial arrangement of the patient'steeth, the second dental model actually precedes the first dental modelin that the patient's teeth, during treatment with the appliance, willreach the second arrangement prior to arriving at the first arrangement.

The appliance, still reflecting the first model arrangement, is securedon the second dental model, and the model and the appliance are placedunder pressure and heated to a second molding temperature (Step 422).The model and appliance are maintained at the second molding temperatureand pressure for a period of time. The temperature is decreased(preferably isobarically) to create an appliance having a second storedgeometry corresponding generally to the dental arrangement representedby the second model (Step 424).

Heating the appliance to the second molding temperature disrupts atleast a portion of the crystalline structures formed during the moldingof the appliance in the first geometry. The second molding temperatureis selected so that the appropriate number of these crystallites aredestroyed. The second molding temperature can be the same or different(i.e., cooler or hotter) than the first molding temperature. Typically,the second molding temperature is cooler than the first moldingtemperature. In such embodiments, the second molding temperature is atleast 1, at least 2, at least 3, at least 4, at least 5° C. less thanthe first molding temperature. In other embodiments, the second moldingtemperature is no more than 10, no more than 5, and no more than 2° C.warmer than the first molding temperature. In certain embodiments, thesecond molding temperature is between 100 and 120° C.

A second plurality of crystalline structures are formed in the polymericmaterial as the temperature is reduced from second molding temperatureto a subsequent temperature (e.g., room temperature). The crystallinestructures formed hold the appliance in the second stored geometry.

Next, a third stored geometry is created in the appliance. A thirdphysical, dental model of the patient's teeth in a preceding successivearrangement from the patient's treatment plan is provided (Step 430).The third arrangement includes a least one tooth in a different positionor orientation than the same tooth in the second model. The third dentalmodel provides a third storable geometry representing an arrangement ofthe patient's teeth between the initial arrangement and the secondarrangement. The third dental model actually precedes the second dentalmodel in that the patient's teeth, during treatment with the appliance,will reach the third arrangement prior to arriving at the secondarrangement.

The appliance, now reflecting the second model arrangement, is securedon the third dental model, and the model and the appliance are placedunder pressure and heated to a third molding temperature cooler than thesecond molding temperature (Step 432). The model and appliance aremaintained at the third molding temperature and pressure for a period oftime. The temperature is decreased (preferably isobarically) to roomtemperature to create an appliance having a third stored geometrycorresponding to the shapes and orientations of teeth in the thirddental model (Step 434).

In some or all embodiments, the third molding temperature is at least 4,at least 6, at least 7, at least 8, at least 9, and at least 10° C., atleast 15° C. less than the second molding temperature. In certainembodiments, the third molding temperature is between 90 and 100° C. Athird plurality of crystallites are formed in the polymeric material asthe temperature is reduced from third molding temperature to asubsequent temperature (e.g., room temperature). The crystallinestructures formed hold the appliance in the third stored geometry untiltriggered according to methods discussed below. An insufficiently largegap in second and third molding temperatures (and between any subsequentmolding temperatures) can have two consequences for continuous memoryappliances: 1) a user or practitioner may inadvertently transition theappliance to a subsequent geometry by heating above the requisitemolding temperature and 2) the desired arrangement may not be adequatelystored in the appliance, as an adequate portion of crystallites are notretained during the corresponding formation.

If the third arrangement is the desired commencing arrangement of thepatient's treatment plan, then the molding process may be finished (Step440). If not, the process 400 of storing geometries corresponding todifferent dental arrangements in an appliance can be repeated as manytimes as desired until the commencing arrangement is stored in theappliance. One skilled in the art may vary the differences between givensuccessive tooth arrangements to expand or contract the length of timethe patient wears a given configuration before needing to transition tothe next appliance configuration. In some embodiments, the appliance canbe manufactured to store at least 4, at least 6, at least 10, at least20, and at least 30 distinct appliance geometries.

Dental models representing the target and successive dental arrangementscan be fabricated by manually forming, sectioning, and re-assembling aphysical dental casting. If the target dental arrangement is defined asan intermediate or final arrangement, then this casting may be sectionedinto individual model tooth elements, and the tooth elements can berearranged to form the desired dental arrangement. Further, the toothelements can be waxed back together to provide the dental model.

Digital techniques can also be used. For example, a final dentalarrangement can be determined using a computer algorithm or input from atreating professional in a treatment plan as described above, and one ormore intermediate dental arrangements derived by sub-dividing thetreatment into a series of discrete steps can be created. In one or moreembodiments, one or more of the dental arrangements can include areduced image as is described, e.g., in U.S. Patent Publication No.2010/0260405 (Cinader). Once each intermediate or final dentalarrangement has been derived, respective dental models may be directlyfabricated using rapid prototyping methods. Examples of rapidprototyping techniques include, but are not limited to,three-dimensional (3D) printing, selective area laser deposition orselective laser sintering (SLS), electrophoretic deposition,robocasting, fused deposition modeling (FDM), laminated objectmanufacturing (LOM), stereolithography (SLA) and photostereolithography.These and other methods of forming a positive dental model from scanneddigital data are disclosed, e.g., in U.S. Pat. No. 8,535,580 (Cinader).

In one or more embodiments, the dental model can also be areconfigurable dental model, thereby allowing individual teeth models tobe rearranged without sectioning. Examples of reconfigurable dentalmodels are described, e.g., in U.S. Pat. No. 6,227,851 (Chishti et al.),U.S. Pat. No. 6,394,801 (Chishti et al.), and U.S. Pat. No. 9,259,295(Christoff et al.). The reconfigurable dental model may be manuallycontrolled (e.g., relying on a technician or other user to repositionindividual teeth) or computer controlled. Use of a computer controlledreconfigurable dental model can be particularly advantageous in certaincircumstances, as the individual teeth can be moved at a deliberate rateduring the forming process as described in more detail below.

In one embodiment of the present invention, a single dental model systemis manipulated and reconfigured to model different tooth configurationsby controlling the movement of at least some of the individual toothmembers, or groups of members, with manipulation mechanisms. Referringto FIG. 5, a simplified illustration of such a reconfigurable dentalmold 500 for the fabrication of dental appliances is shown. In thisillustration, the mold 500 is a positive representation of the toothconfiguration and dental arch of the lower jaw. The tooth configurationis created by the placement and alignment of tooth members 501. Theindividual tooth members 501 are typically produced to resemble theindividual shape of each of the patient's teeth.

The tooth members 501 are supported by a frame 502, which can housemanipulation mechanisms for controlling the position and orientation ofthe tooth members within the arch. The tooth members 501 and frame 502of the dental model system may be produced manually or with the use ofdigital imaging and computer controlled molding systems.

The frame houses one or more manipulation devices 511 which manipulatethe tooth members 501. Once coupled to the manipulation devices 511, thetooth members 501 can be actuated and repositioned. The manipulationdevice 511 can be a single mechanism, linked simultaneously to eachindividual tooth member 501 or group of members using, for example, aseries of mechanical linkages. Optionally, the tooth members 501 can beactuated by a combination of manipulation devices each providing somedegree of manipulation within a given coordinate system.

The manipulation devices 511, which create the actual six degree offreedom movement of the tooth members 501, may be controlled manuallyand/or with the use of a microprocessor. In one embodiment, therepositioning of the individual tooth members 501 involves at least someof the components of manipulation device 511 being manually operated. Inthis embodiment, the practitioner will manually actuate each controlmechanism, usually with finger pressure, which will in turn actuate theinner components of the manipulation device until a desired tootharrangement is produced. Likewise, manual operation may be assisted withthe visual aide of computer graphics or with instructions provided bysoftware code.

In presently preferred embodiments, manipulation of manipulation devices511 can be performed using a computer 600 or a workstation having asuitable graphical user interface (GUI) 601. In a specific example shownin FIG. 5, computer 600 is electrically coupled to manipulation device511 to enable computer generated instructions to be sent to manipulationdevices 511 via appropriate computer coupling methods, represented asline 602. The manipulation of tooth members 501 is driven using softwareappropriate for viewing and modifying the images (see above) on the GUI601, as well as directing and controlling the tooth movements accordingto the treatment plan.

When using the reconfigurable dental mold 500 to produce one or a seriesof continuous memory appliances for orthodontic treatment, the mold 500may be manipulated through a series of tooth configurations representinga planned successive arrangement and a corresponding stage inorthodontic treatment. As described previously, the initial toothconfiguration is represented by digital information and is introduced tocomputer 600 for manipulation of the mold 500. Once the user issatisfied with the final arrangement of teeth, the final tootharrangement is incorporated into a final digital data set. Based on oneor more of the data sets, and optionally user input, a plurality ofintermediate, successive digital data sets are generated to correspondto successive intermediate tooth arrangements and stored in mediumaccessible to computer 600.

The user of the reconfigurable mold may then direct the software to sendan instruction to a manipulation device 611 to direct a tooth member 601to move to a position which corresponds to a position digitallyrepresented in a planned successive data set or target data set. Afterthe tooth members 601 are each manipulated and arranged to correspond tothe data, the dental model system can be used to fabricate thecontinuous memory appliance.

In certain embodiments of the process 400 for creating a continuousmemory appliance, the dental models are provided in discrete stages. Insuch embodiments, the appliance may be removed from the correspondingdental model after each cooling step. The dental model of arrangement(n) is then replaced with a distinct dental model of a precedingintermediate arrangement of the treatment plan (n-1), or the toothmembers in a reconfigurable dental model are manipulated and arranged tocorrespond to the preceding, planned successive arrangement (n-1). Oncethe dental model representing the preceding, planned arrangement is soprovided, the appliance is placed over the new arrangement and a newplurality of crystallites are formed.

Alternatively, and in presently preferred embodiments, the appliancestructure is kept in contact with a reconfigurable dental moldthroughout the duration of the process for storing treatment geometries,as set out as process 700 in FIG. 6. In such embodiments, the polymericmaterial is kept under pressure as the dental mold is reconfigured toeach desired dental arrangement. Typically, the appliance is firstconfigured to represent the target arrangement and crosslinked to setthe original shape before storing the desired series of successivearrangements (Step 702). This initial configuration can be done on thereconfigurable dental mold or a static mold (e.g., as used in process400 above). A reconfigurable dental mold of a planned precedingarrangement (a second arrangement relative to the original shape) isprovided (Step 704). The reconfigurable model in the second arrangementand the crosslinked appliance in the original shape are placed underpressure and heated to a first molding temperature (Step 706). The modeland appliance are maintained at the first temperature until such time asthe sheet has conformed to the shape and orientation of the dental modelin the second arrangement (Step 708). The temperature is decreased(preferably isobarically) to a second molding temperature (Step 710).The mold is then reconfigured to a planned preceding arrangement (athird arrangement), causing a deformation of the crosslinked appliance(Step 712). In presently preferred circumstances, a processor operatingsuitable software sends instructions or otherwise directs the individualteeth of the reconfigurable mold to move to the relevant arrangement.The movement may be prompted by a user operating a computer or beprogrammed to occur at least semi-automatically. The mold and applianceare maintained at the second temperature until such time as the sheethas conformed to the shape and orientation of the dental mold in thethird arrangement, creating an appliance in a configuration having athird stored geometry corresponding to the third arrangement (Step 714).

The appliance structure and reconfigurable dental mold are maintained ineach planned arrangement at the requisite molding temperature for aperiod of time sufficient to allow for a steady state ofcrystallization. This period may be dependent on the polymeric materialin the appliance and the first molding temperature. In presentlypreferred implementations, the pressure is decreased subsequently to therearrangement of the dental mold, or at slower rate than the movement ofindividual tooth members of the mold in reaching the second arrangement.The tooth members in the reconfigurable mold can be moved betweenarrangements at any desired rate (e.g., 0.5 mm/min), so long as thevelocity does not irreversibly degrade the polymeric material. Theprocess 700 is repeated until the appliance has a configurationrepresenting the desired commencing arrangement and has stored allplanned successive arrangements between the commencing arrangement andthe target arrangement (Step 716).

Advantageously, the method of manufacturing 700 allows the appliance toaccommodate the entire movement path of each tooth moved between thecommencing arrangement and the target arrangement. Accommodation of thefull path of movement can, in certain circumstances, ensure the forceapplied to reposition the tooth remains relatively constant betweenstages, even as the appliance deforms while worn on the patient's dentalarch. Furthermore, the use of a single mold with continuous movementreduces manufacturing time and cost, as individual models representingeach planned successive arrangement do not have to be created andswapped out at each storage stage. For example, a complete sequence ofappliances can be made using only a sufficient amount of polymericmaterial to form a single tray. The reconfigurable dental mold can alsobe reused during the course of treatment if the orthodontic practitionerdetermines that one or more additional intermediate appliances would bebest for additional treatment.

Appliances may also be fabricated with special features requested by thepractitioner, such as buttons and windows to assist certain teethmovement. For example, buttons and windows may be used to help securethe appliances to the patient's dental arch, and may be used to directforce to move the teeth of the dental arch. For example, if suchfeatures are requested, small buttons can be installed on the modelteeth in the manufacturing process. A template plastics tray will bemade to assist the doctors to place the buttons in a subject's teeth.Appliances can then be fabricated with windows (e.g., small cut-outs) atthe location of each prescribed button. In some cases, it may beadvantageous to use a multilayer material with one layer providingcontinuous shape memory properties and the other layer providingenhanced physical properties, such as stiffness and abrasion resistance.In a multilayer system, the elastic recovery force of the shape memorymaterial (e.g., the semicrystalline polymeric material) can be designedto be sufficient to deform the other material at the temperatures ofinterest, and the relative thicknesses of the two layers can be chosenachieve this balance. The second, non-memory layer can have a transitiontemperature between use temperature and the transition temperature rangeof the shape memory polymer to allow it to be deformed by the shapememory material. Suitable methods for design and manufacture ofmultilayer shell appliances can be found, for example, in U.S. Pat. No.8,758,009 (Chen et al.).

Manufacturing may include post-processing to remove uncured resin andremove support structures, or to assemble various components, which mayalso be necessary and could also be performed in a clinical setting.

Treatment Using a Continuous Memory Appliance

Referring now to FIG. 7, a method of treatment 800 using an appliance(particularly a shell appliance) of the present disclosure is depicted.An adjustment appliance having an original shape and at least threestored successive geometries is provided to the patient in thecommencing arrangement (Step 802). It should be appreciated that anappliance could be provided having 2 or fewer stored geometries inaddition to the original shape, and such embodiments may include oneless heating and wear step. Similarly, an adjustment appliance may beprovided with more, even considerably more, than three or four storedgeometries, in which case the treatment process may include additionalheating and wear steps commensurate with the number of storedgeometries. In any event, the patient (or practitioner) first places theappliance on his or her dental arch and the appliance is worn forprescribed period of time to define a first wear period (Step 804). Atthe end of first wear period, the patient (or practitioner) removes theappliance from the mouth and heats appliance to a temperature above themolding temperature used to create the commencing arrangement in theappliance (Step 806). The heating destroys a portion of the formedcrystal structures to unlock or transition to a second stored appliancegeometry representing a successive intermediate arrangement in thepatient's treatment plan. The appliance is then cooled, typically backto room temperature.

While an adequate increase in the temperature of the appliance can beused to selectively destroy crystalline structures in the appliance, anexcess increase in temperature can result in the inadvertent partial orcomplete destruction of a successive stored geometry. Typically, theappliance is heated to no greater than 6° C. above the correspondingmolding temperature, in some embodiment no greater than 5, in someembodiments no greater than 3, and in some embodiments not greater than1° C. above the corresponding molding temperature. In certain typicalimplementations, the appliance is heated to a temperature of 80° C. to95° C. to transition to the second stored geometry.

Patient (or practitioner) subsequently places the appliance, nowrepresenting the second geometry, on the dental arch and wears the shellfor a prescribed period of time (Step 808). At end of prescribed period,the patient (or practitioner) again heats the appliance to a temperatureabove the molding temperature used to form the appliance in the firstsuccessive intermediate arrangement (i.e., the second stored geometry)(Step 810). The heating destroys an additional portion of the formedcrystal structures to unlock or otherwise transition to a third storedappliance geometry representing a successive intermediate arrangement inthe patient's treatment plan. In certain typical implementations, theappliance is heated to a temperature of 95° C. to 110° C. to transitionto the third stored geometry.

The patient (or practitioner) subsequently places the appliance, nowrepresenting the third geometry, on the dental arch and wears the shellfor prescribed period of time (Step 812). At end of prescribed period,the patient (or practitioner) again heats appliance to a temperatureabove the molding temperature used to form the appliance in the secondsuccessive intermediate arrangement (i.e., the third stored geometry)(Step 814). The heating destroys an additional portion of the formedcrystal structures to unlock or otherwise transition to a fourth storedappliance geometry representing the original shape. In certain typicalimplementations, the appliance is heated to a temperature of 110° C. to120° C. to transition to the original shape.

Each stored geometry in the appliance can be recovered using heatsources such as a hot air gun, hot plate, steam, conventional oven,infrared heater, radiofrequency (R f) sources or microwave sources.Alternatively, the appliance can be immersed in a heated bath containinga suitable inert liquid (for example, water or a fluorochemical fluid)that will not dissolve or swell the appliance in either its cool or warmstates. The appliance can be encased in a plastic pouch or othercontainer which is in turn heated (e.g., electrically), or subjected toone or more of the above-mentioned heating methods. Once heated and heldat the appropriate temperature, the appliance is preferably cooled tobody temperature (37° C.) or below to lock in the intended configurationand to avoid discomfort or injury.

After wearing the appliance having the fourth stored geometry for aprescribed period of time (Step 816), the patient may return to thepractitioner who may evaluate the result of the first iteration oftreatment (Step 818). In the event that the first iteration of treatmenthas resulted in satisfactory final placement of the patient's teeth, thetreatment may be ended. However, if the first iteration of treatment didnot complete the desired movement of the patient's teeth, one or moreadditional iterations of treatment may be performed. To begin the nextiteration of treatment, the practitioner may taking another scan of thepatient's teeth are taken to facilitate the design of the ordered set ofremovable dental appliances. In some examples, evaluation of the resultof the first iteration of treatment may include taking another scan ofthe patient's teeth, in which case beginning the next iteration oftreatment may simply involve forwarding the digital model of thepatients teeth to a manufacturing facility so that another adjustmentappliance or series of adjustment appliance may be manufactured for thepatient based on the new positions of the patient's teeth. In yet otherexamples, the newly acquired scan may be used to create one or moreiterations of adjustment appliances in the practitioner's facility.

In one or more embodiments that utilize progressive treatment of apatient's teeth, second, third, or more intermediate scans of the teethcan be performed using any suitable technique or combination oftechniques. The practitioner or manufacturer can then utilize theseintermediate scans to provide one or more additional appliances that areadapted to provide one or more corrective forces to the teeth such thatone or more teeth are repositioned to either a subsequent intermediatearrangement or a final target arrangement. Any suitable technique orcombination of techniques can be utilized to provide these intermediatescans, models, and arch members, e.g., the techniques described in U.S.Patent Application Publication No. 2010/0260405 (Cinader) andInternational Publication WO2016/109660 (Raby et al.).

Various techniques of this disclosure may be implemented in a widevariety of computer devices, such as servers (including the Cloud),laptop computers, desktop computers, notebook computers, tabletcomputers, hand-held computers, smart phones, and the like. Anycomponents, modules or units have been described to emphasize functionalaspects and does not necessarily require realization by differenthardware units. The techniques described herein may also be implementedin hardware, software, firmware, or any combination thereof. Anyfeatures described as modules, units or components may be implementedtogether in an integrated logic device or separately as discrete butinteroperable logic devices. In some cases, various features may beimplemented as an integrated circuit device, such as an integratedcircuit chip or chipset. Additionally, although a number of distinctmodules have been described throughout this description, many of whichperform unique functions, all the functions of all of the modules may becombined into a single module, or even split into further additionalmodules. The modules described herein are only exemplary and have beendescribed as such for better ease of understanding.

If implemented in software, the techniques may be realized at least inpart by a non-transitory computer-readable medium comprisinginstructions that, when executed in a processor, performs one or more ofthe methods described above. The computer-readable medium may comprise atangible computer-readable storage medium and may form part of acomputer program product, which may include packaging materials. Thecomputer-readable storage medium may comprise random access memory (RAM)such as synchronous dynamic random access memory (SDRAM), read-onlymemory (ROM), non-volatile random access memory (NVRAM), electricallyerasable programmable read-only memory (EEPROM), FLASH memory, magneticor optical data storage media, and the like. The computer-readablestorage medium may also comprise a non-volatile storage device, such asa hard-disk, magnetic tape, a compact disk (CD), digital versatile disk(DVD), Blu-ray disk, holographic data storage media, or othernon-volatile storage device. The term “processor,” as used herein mayrefer to any of the foregoing structure or any other structure suitablefor implementation of the techniques described herein. In addition, insome aspects, the functionality described herein may be provided withindedicated software modules or hardware modules configured for performingthe techniques of this disclosure. Even if implemented in software, thetechniques may use hardware such as a processor to execute the software,and a memory to store the software. In any such cases, the computersdescribed herein may define a specific machine that is capable ofexecuting the specific functions described herein. Also, the techniquescould be fully implemented in one or more circuits or logic elements,which could also be considered a processor.

Embodiments

1. A polymeric shell dental appliance for placement on a dental archcomprising a concave trough having a cavity configured to be positionedon a plurality of teeth in the dental arch and having a firstapproximate shape, wherein the concave trough comprises a crosslinkedshape memory polymer, and wherein the crosslinked shape memory polymeris a semicrystalline, non-segmented polymer configured to restore theconcave trough to (a) a second approximate shape on application of afirst external energy stimulus; and (b) a third approximate shape onapplication of a second external energy stimulus of a greater magnitudethan the first energy stimulus.

2. The polymeric shell dental appliance of embodiment 1, wherein thethird approximate shape represents a prescribed final arrangement of theteeth in the dental arch.

3. The polymeric shell dental appliance of embodiment 1, wherein thesecond approximate shape represents an intermediate arrangement of teethin the dental arch.

4. The polymeric shell dental appliance of any of the prior embodiments,wherein each external energy stimulus is an increase in temperature.

5. The polymeric shell dental appliance of embodiment 4, wherein eachexternal energy stimulus represents a transition temperature, andwherein each transition temperature is greater than 37° C.

6. The polymeric shell dental appliance of any one of the previousembodiments, wherein the crosslinked shape memory polymer is furtherconfigured to restore the concave trough to a fourth approximate shapeon application of a fourth external energy stimulus of a greatermagnitude than the second or third energy stimuli.

7. The polymeric shell of any of the previous embodiments, wherein theshell includes an outer layer and an inner layer, and wherein the innerlayer comprises the crosslinked shape memory polymer.

8. The polymeric shell of any of the previous embodiments, wherein thepolymer contains physical crosslinks, chemical crosslinks, orcombinations thereof

9. The polymeric shell appliance of embodiment 1, wherein thesemicrystalline polymeric material includes a number of crystallinestructures, and wherein a portion of crystalline structures areirreversibly disrupted on application of the first external energystimulus to transition the shell to the second approximate shape.

10. The polymeric shell appliance of embodiment 9, wherein the remainingportion of crystalline structures are irreversibly disrupted onapplication of the third external energy stimulus.

11. The polymeric shell appliance of any of the previous embodiments,wherein the polymer includes a crystallization temperature range, andwherein recovery of the second and third approximate shapes occurs whenthe temperature of the shell is increased to a corresponding temperaturewithin the crystallization temperature range. 12. The polymeric shellappliance of embodiment 11, wherein the semicrystalline polymericmaterial includes a number of crystalline structures, wherein anincreasing number of crystalline structures are irreversibly disruptedas the temperature of the shell is increased through the crystallizationtemperature range.

13. The polymeric shell appliance of embodiment 12, wherein irreversiblydisrupting the crystalline structures changes the approximate shape ofthe shell, the cavities within the trough, and a combination thereof

14. The polymeric shell appliance of any of the previous embodiments,wherein crosslinked shape memory polymer is selected from polyethylene,ethylene vinyl acetate, and combinations thereof

15. A method for manufacturing polymeric shell dental appliancesconfigured to conform to one or more teeth of a patient, the methodcomprising: providing a first positive model of the patient's dentition,the model representing a repositioned arrangement of the patient'steeth; forming over the model at a first molding temperature a sheet ofcrosslinkable, crystallizable polymeric material having acrystallization temperature range having an upper limit and a lowerlimit; crosslinking the polymer to create an appliance having a firststored geometry; providing a second model representing a firstintermediate arrangement of the patient's teeth, the arrangementincluding one or more teeth in different orientations than the firstmodel; subjecting the appliance to a second molding temperature withinthe crystallization temperature range and being less than the firstmolding temperature to create a shell having a second stored geometry;providing a third model representing a second intermediate arrangementof the patient's teeth, the second arrangement including one or moreteeth in different orientations than the first intermediate arrangement;subjecting the appliance to a third molding temperature within thecrystallization temperature range to create a third stored geometry, thethird molding temperature being less than either the first or secondmolding temperatures; and cooling the shell below the lower limit oftransition temperature range.

16. The method of embodiment 15, wherein the shape memory material isselected from polyethylene, ethylene vinyl acetate, and combinationsthereof.

17. The method of embodiment 15 or 16, wherein heating the sheetcomprises heating for a period of time sufficient to selectively melt atleast portion of the crystalline structures in the shape memorymaterial.

18. The method of any of the previous embodiments, wherein the shapememory material is physically crosslinkable, chemically crosslinkable,or combinations thereof.

19. The method of any of the previous embodiments and further comprisingsubjecting the appliance in the first stored geometry to irradiation tocreate a number of chemical crosslinks in the shape memory material.

20. The method of embodiment 19, wherein the irradiation is selectedfrom gamma, E-beam, and combinations thereof.

21. The method of any of the previous embodiments, and furthercomprising:

creating a first series of crystalline structures in the shape memorypolymer while the shell has the second stored geometry.

22. The method of any of the previous embodiments, wherein the firstmodel comprises a plurality of reconfigurable tooth models arrangedrelative to a physical arch, and wherein providing the second modelcomprises moving at least one of the tooth objects to create the secondarrangement.

23. The method of embodiment 22, wherein moving at least one of thetooth objects comprises moving the tooth object along a treatment path.

24. The method embodiment 23, and further comprising placing the firstmodel within a temperature controlled chamber and reducing thetemperature in the chamber from the first molding temperature to thesecond molding temperature, and wherein the tooth model is moved alongthe treatment path segment while the temperature in the chamber isreduced from the first molding temperature to the second moldingtemperature.

25. The method of any of the previous embodiments, wherein the forming asheet of polymeric material over the model includes the act of applyingpressure to the model.

26. The method of embodiment 25, wherein the forming a sheet ofcrosslinkable polymeric material over the model includes the act ofapplying pressure to the model, and wherein the tooth model is movedalong the treatment path segment while the pressure is applied to themodel.

27. The method of any of the previous embodiments, wherein the polymericmaterial forms an increasing number of crystalline structures as thetemperature is reduced from the upper limit of the crystallizationtemperature range to the lower limit.

28. The method of any of the previous embodiments, wherein the steps ofproviding the first, second, and third positive models each compriseproviding a printed model of the dentition representing the desiredarrangement of the patient's teeth.

29. The method of any of the previous embodiments, wherein each moldingtemperature is greater than 37° C.

30. A method of moving a patient's teeth of a target arrangement, themethod comprising: placing an orthodontic appliance having a firstconfiguration on a dental arch, the orthodontic appliance comprising acrosslinked, semicrystalline shape memory polymer having a number ofcrosslinks and crystalline structures; heating the appliance to a firsttransition temperature so as to modify the shape of the shell to asecond configuration; placing the appliance in the second configurationon the dental arch; heating the appliance to a second transitiontemperature so as the modify the shape of the shell to a thirdconfiguration; placing the appliance in the third configuration on thedental arch; the third configuration shaped to reposition the patient'steeth to the target arrangement.

31. The method of embodiment 30, wherein heating the appliance to afirst transition temperature disrupts a portion of the crystallinestructures in the shape memory polymer.

32. The method of embodiment 31, wherein heating the appliance to asecond transition temperature disrupts at least a portion of theremaining crystalline structures in the shape memory polymer.

33. The method of embodiments 30-32, wherein the appliance comprises ashell that includes an inner cavity including a plurality ofreceptacles, and wherein heating the polymeric shell to a firsttransition temperature so as to modify the shape of the shell to asecond configuration comprises modify the position of at least onereceptacle within the cavity.

34. The method of embodiments 30-33, wherein the first transitiontemperature is about 80° C.

35. The method of embodiments 30-34, wherein the third transitiontemperature is about 120° C.

All of the patents and patent applications mentioned above are herebyexpressly incorporated by reference. The embodiments described above areillustrative of the present invention and other constructions are alsopossible. Accordingly, the present invention should not be deemedlimited to the embodiments described in detail above and shown in theaccompanying drawings, but instead only by a fair scope of the claimsthat follow along with their equivalents.

1. A polymeric shell dental appliance for placement on a dental archcomprising a concave trough having a cavity configured to be positionedon a plurality of teeth in the dental arch and having a firstapproximate shape, wherein the concave trough comprises a crosslinkedshape memory polymer, and wherein the crosslinked shape memory polymeris a semicrystalline, non-segmented polymer configured to restore theconcave trough to (a) a second approximate shape on application of afirst external energy stimulus; and (b) a third approximate shape onapplication of a second external energy stimulus of a greater magnitudethan the first energy stimulus.
 2. The polymeric shell dental applianceof claim 1, wherein the third approximate shape represents a prescribedfinal arrangement of the teeth in the dental arch.
 3. The polymericshell dental appliance of claim 1, wherein the second approximate shaperepresents an intermediate arrangement of teeth in the dental arch. 4.The polymeric shell dental appliance of claim 1, wherein each externalenergy stimulus is an increase in temperature.
 5. The polymeric shelldental appliance of claim 4, wherein each external energy stimulusrepresents a transition temperature, and wherein each transitiontemperature is greater than 37° C.
 6. The polymeric shell dentalappliance of claim 1, wherein the crosslinked shape memory polymer isfurther configured to restore the concave trough to a fourth approximateshape on application of a fourth external energy stimulus of a greatermagnitude than the second or third energy stimuli.
 7. The polymericshell of claim 1, wherein the polymer contains physical crosslinks,chemical crosslinks, or combinations thereof.
 8. The polymeric shellappliance of claim 1, wherein the semicrystalline polymeric materialincludes a number of crystalline structures, and wherein a portion ofcrystalline structures are irreversibly disrupted on application of thefirst external energy stimulus to transition the shell to the secondapproximate shape.
 9. The polymeric shell appliance of claim 8, whereinthe remaining portion of crystalline structures are irreversiblydisrupted on application of the third external energy stimulus.
 10. Thepolymeric shell appliance of claim 1, wherein the polymer includes acrystallization temperature range, and wherein recovery of the secondand third approximate shapes occurs when the temperature of the shell isincreased to a corresponding temperature within the crystallizationtemperature range.
 11. The polymeric shell appliance of claim 10,wherein the semicrystalline polymeric material includes a number ofcrystalline structures, wherein an increasing number of crystallinestructures are irreversibly disrupted as the temperature of the shell isincreased through the crystallization temperature range, and whereinirreversibly disrupting the crystalline structures changes at least oneof the approximate shape of the shell, the cavities within the trough,and a combination thereof.
 12. A method for manufacturing polymericshell dental appliances configured to conform to one or more teeth of apatient, the method comprising: providing a first positive model of thepatient's dentition, the model representing a repositioned arrangementof the patient's teeth; forming over the model at a first moldingtemperature a sheet of crosslinkable, crystallizable polymeric materialhaving a crystallization temperature range having an upper limit and alower limit; crosslinking the polymer to create an appliance having afirst stored geometry; providing a second model representing a firstintermediate arrangement of the patient's teeth, the arrangementincluding one or more teeth in different orientations than the firstmodel; subjecting the appliance to a second molding temperature withinthe crystallization temperature range and being less than the firstmolding temperature to create a shell having a second stored geometry;providing a third model representing a second intermediate arrangementof the patient's teeth, the second arrangement including one or moreteeth in different orientations than the first intermediate arrangementsubjecting the appliance to a third molding temperature within thecrystallization temperature range to create a third stored geometry, thethird molding temperature being less than either the first or secondmolding temperatures; and cooling the shell below the lower limit oftransition temperature range.
 13. The method of claim 12, whereinheating the sheet comprises heating for a period of time sufficient toselectively melt at least portion of the crystalline structures in theshape memory material. 14.-15. (canceled)
 16. The method of claim 12,wherein the first model comprises a plurality of reconfigurable toothmodels arranged relative to a physical arch, and wherein providing thesecond model comprises moving at least one of the tooth objects tocreate the second arrangement.
 17. The method of claim 16, wherein theforming a sheet of crosslinkable polymeric material over the modelincludes the act of applying pressure to the model, and wherein thetooth model is moved along a treatment path segment while the pressureis applied to the model.
 18. The method of claim 12, wherein thepolymeric material forms an increasing number of crystalline structuresas the temperature is reduced from the upper limit of thecrystallization temperature range to the lower limit. 19.-21. (canceled)